If you bring a deal must be yours/Control It/ Mandate to it (OFF MARKET ONLY)4.

If you’re not in the city of LA see what city you are in and the rent control for that city.

If it’s really outside the seller’s control, there’s not a whole lot you can do other than maybe walk away and get your Deposit back.

I can think of some ways to calculate how much of their electric the furnace has used based on the gas bill and some electrical testing, but nothing that quick or precise. 

The key is that the QI must be involved in the purchase prior to closing, the Purchase and Sale Agreement (and any escrow related documents) must be assigned to the QI so that the QI is now acting as the seller before closing so that when they wire the funds to the closing they are really wiring funds to a closing that the QI has control over as the seller. 

With you designing though, you might be able to control these costs a little more.3.

How to control what you leave in the deal?

The question is how involved do you want to get with your investments and how much control do you want?

If you want to get control of this property so you can sell a different property and 1031 into the property you control then the answer is totally different.  

Understand what they're charging per sq ft so you are more precise when running your numbers online.